1. Field of the Invention
This invention relates to an injection molding unit for use in an injection molding machine for processing synthetic materials comprising a plasticizing cylinder, which is mounted in a carrier block, a driving unit, such as a mechanical driving unit, for axial displacement of the injection molding unit in a direction of an injection axis, an injection unit, such as a mechanical injection unit, arranged symmetrically with respect to the injection axis, adapted to axially drive a feeding means located in the plasticizing cylinder and an injection bridge connected with the injection unit.
2. Description of the Prior Art
European Published Patent Application EP-A-328671 discloses an injection unit of that kind, in which electromechanical spindle drives are provided for axial displacement of the feed screw and for contacting the nozzle to the injection mold. In such an arrangement, however, only the force initiation for the axial movement of the feed screw is effected symmetrically with respect to the injection axis, whereas the displacement of the injection molding unit is effected asymmetrically with respect to the injection axis, so that distortions might occur when the nozzle is contacted. Since an abutment for the driving unit is provided at the machine base for the movement of the injection molding unit, it requires a lot of installation work to transfer the injection molding unit, for example, into a vertical position where it can inject into the parting plane or to make it accessible to a linear gating.
A further injection molding unit of that kind is also known from European Published Patent Application 0 427 866, in which a ball rolling spindle is mounted at a stationary plate in such a way, that a second plate is axially displaced during rotation of the spindles. The second plate is connected with the feed screw, so that the axial movement effects the axial displacement of the feed screw. In this arrangement the driving unit for displacement of the whole injection molding unit is understood not to be a part of the injection molding unit itself and for that reason the injection molding unit itself can only be driven from the outside. The contact forces for the nozzle act outside the injection axis and separate guidings are necessary for the movement of the injection molding unit.
The leaflet Fanuc Autoshot T series, model 50D/75D/100D/150D/225D/300D, page 8, discloses an injection molding unit, in which spindle drives, driven by toothed belts, are provided for the injection process. However, in this unit separate guidings, located outside, are provided as guiding elements for the injection molding unit and for displacement of the injection bridge.
Finally, in the field of hydraulic driven injection molding units, German Utility Model 70 46 626 discloses an arrangement, in which the driving unit, symmetrically arranged with respect to the injection axis, and the injection molding unit are nested. However, this type of construction obviously did not give incitations for the field of electromechanical drives or hybrid machines, in which one unit is driven electromechanically and the other hydraulically.